• Journal of Soil and Groundwater Environment
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• v.24 no.3
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• pp.24-35
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• 2019

It is known that ${\delta}^{13}C_{DIC}$ (carbon-13 isotope of dissolved inorganic carbonate (DIC) ions) of water increases when dissolved $CO_2$ degases. However, ${\delta}^{13}C_{DIC}$ could decrease when the pH of water is lower than 5.5 at the early stage of degassing. Laboratory experiments were performed to observe the changes of ${\delta}^{13}C_{DIC}$ as $CO_2$ degassed from three different artificial $CO_2$-rich waters (ACWs) in which the initial pH was 4.9, 5.4, and 6.4, respectively. The pH, alkalinity and ${\delta}^{13}C_{DIC}$ were measured until 240 hours after degassing began and those data were compared with kinetic isotope fractionation calculations. Furthermore, same experiment was conducted with the natural $CO_2$-rich water (pH 4.9) from Daepyeong, Sejong City. As a result of experiments, we could observe the decrease of DIC and increase of pH as the degassing progressed. ACW with an initial pH of 6.4, ${\delta}^{13}C_{DIC}$ kept increasing but, in cases where the initial pH was lower than 5.5, ${\delta}^{13}C_{DIC}$ decreased until 6 hours. After 6 hours ${\delta}^{13}C_{DIC}$ increased within all cases because the $CO_2$ degassing caused pH increase and subsequently the ratio of $HCO_3{^-}$ in solution. In the early stage of $CO_2$ degassing, the laboratory measurements were well matched with the calculations, but after about 48 hours, the experiment results were deviated from the calculations, probably due to the equilibrium interaction with the atmosphere and precipitation of carbonates. The result of this study may be not applicable to all natural environments because the pressure and $CO_2$ concentration in headspace of reaction vessels was not maintained constant as well as the temperature. Nevertheless, this study provides fundamental knowledge on the ${\delta}^{13}C_{DIC}$ evolution during $CO_2$ degassing, and therefore it can be utilized in the studies about carbonated water with low pH and the monitoring of geologic carbon sequestration.

• Journal of Soil and Groundwater Environment
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• v.14 no.3
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• pp.1-13
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• 2009

Alkalinity and total carbon contents were measured by acid neutralizing titration (ANT), back titration (BT), gravitational weighing (GW), non-dispersive infrared-total carbon (NDIR-TC) methods for assessing precision and accuracy of alkalinity and total carbon concentration in $CO_2$-rich water. Artificial $CO_2$-rich water(ACW: pH 6.3, alkalinity 68.8 meq/L, $HCO_3^-$ 2,235 mg/L) was used for comparing the measurements. When alkalinity measured in 0 hr, percent errors of all measurement were 0~12% and coefficient of variation were less than 4%. As the result of post-hoc analysis after repeated measure analysis of variance (RM-AMOVA), the differences between the pair of methods were not significant (within confidence level of 95%), which indicates that the alkalinity measured by any method could be accurate and precise when it measured just in time of sampling. In addition, alkalinity measured by ANT and NDIR-TC were not change after 24 and 48 hours open to atmosphere, which can be explained by conservative nature of alkalinity although $CO_2$ degas from ACW. On the other hand, alkalinity measured by BT and GW increased after 24 and 48 hours open to atmosphere, which was caused by relatively high concentration of measured total carbon and increasing pH. The comparison between geochemical modeling of $CO_2$ degassing and observed data showed that pH of observed ACW was higher than calculated pH. This can be happen when degassed $CO_2$ does not come out from the solution and/or exist in solution as $CO_{2(g)}$ bubble. In that case, $CO_{2(g)}$ bubble doesn't affect the pH and alkalinity. Thus alkalinity measured by ANT and NDIR-TC could not detect the $CO_2$ bubble although measured alkalinity was similar to the calculated alkalinity. Moreover, total carbon measured by ANT and NDIR-TC could be underestimated. Consequently, it is necessary to compare the alkalinity and total carbon data from various kind of methods and interpret very carefully. This study provide technical information of measurement of dissolve $CO_2$ from $CO_2$-rich water which could be natural analogue of geologic sequestration of $CO_2$.

• Economic and Environmental Geology
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• v.32 no.5
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• pp.469-483
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• 1999

Two different types of deep groundwaters occur together in the Jungwon area: $CO_2$-rich water and alkali water. Each water shows distrinct hydrogeochemical and environmental isotopic characteristics. The $CO_2$-rich waters are characterized by lower pH(6.0~6.4), higher Eh (25~85mV) and higher TDS content (up to 3,300 mg/l), whereas the alkali type waters have higher pH (9.1~9.5), lower Eh (-136~-128mV) and lower TDS content (168~254 mg/l). The CO2-rich waters ($Pco_2$=up to 1atm) were probably evolved by the local supply of deep $CO_2$ during the deep circulation, resulting in enhanced dissolution of surrounding rocks to yield high concentrations of $Ca^{2+}, Na^+, Mg^{2+}, K^+\; and \;HCO_3\;^-$ under low pH conditions. On the other hand, the alkali type waters ($Pco_2$=about 10-4.6 atm) were evolved through lesser degrees of simple wate/rock (granite) interaction under the limited suppy of $CO_2$. The alkali waters are relatively enriched in F- (up to 14mg/l), whereas the F- concentration of$CO_2$-rich water is lower (2.2~4.8 mg/l) due to the buffering by precipitation of fluorite. The oxygen-hydrogen isotopes and tritium data indicate that compared to shaltion ($\delta$18O=-9.5~-7.8$\textperthousand$),two different types fo deep groudwaters (<1.0TU)were both derived from pre-thermonuclear (more than 40 years old) meteoric waters with lighter O-H isotopic composition ($\delta$18O=-9.5~-7.8$\textperthousand$) and have evolved through prolonged water/rock interaction. The $CO_2$-rich waters also show some degrees of isotopic re-equilibration with $CO_2$ gas. The $\delta^{34}S$ values of dissolved sulfates (+24.2~+27.6$\textperthousand$) in the $CO_2$-rich waters suggest the reduction of sulfate by organic activity at depths. The carbon isotope data show that dissolved carbon in the $CO_2$-rich waters were possibly derived either from dissolution of calcite or from deep $CO_2$ gas. However, strontium isotope data indicate Ca in the $CO_2$-rich waters were derived mainly from plagioclase in granite, not from hydrothermal calcites.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.8-14
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• 1980

Solvolysis rate constants for methylchloroformate, $CH_3O$(CO)Cl, methylthiono-chloroformate, $CH_3O$(CS)Cl, and methylthiolchloroformate, $CH_3S$(CO)Cl, have been determined conductometrically in acetone-water and acetonitrile-water mixtures, and activation parameters, ${\Delta}H^{\neq}$ and ${\Delta}S^{\neq}$, have been derived. Results show that in water-rich regions the order of rate increases as $$CH_3O(CO)Cl while in dipolar aprotic solvent-rich region this order reverses. The plots of log k vs. solvent parameters, Y, $\frac{D-1}{2D+1}$ and log($H_2$) show that the order of rate increase in water-rich region is the results of increase in $S_N1$ character. It is concluded that $CH_3S$(CO)Cl solvolyzes via $S_N1$ mechanism whereas $CH_3O$(CO)Cl reacts via $S_N2$ and $CH_3O$(CS)Cl via intermediate mechanism in water-rich region.

• Clean Technology
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• v.29 no.1
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• pp.39-45
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• 2023

To investigate the effects of Mg addition at different aging times and temperatures, Cu/MgO/Al₂O₃ catalysts were synthesized for the low-temperature water gas shift (LT-WGS) reaction. The co-precipitation method was employed to prepare the catalysts with a fixed Cu amount of 30 mol% and varied amounts of Mg/Al. Synthesized catalysts were characterized using XRD, BET, and H₂-TPR analysis. Among the prepared catalysts, the highest CO conversion was achieved by the Cu/MgO/Al₂O₃ catalyst (30/40/30 mol%) with a 60 ℃ aging temperature and a 24 h aging time under a CO₂-rich feed gas. Due to it having the lowest reduction temperature and a good dispersion of CuO, the catalyst exhibited around 65% CO conversion with a gas hourly space velocity (GHSV) of 14,089 h-1 at 300 ℃. However, it has been noted that aging temperatures greater or less than 60 ℃ and aging times longer than 24 h had an adverse impact, resulting in a lower surface area and a higher reduction temperature bulk-CuO phase, leading to lower catalytic activity. The main findings of this study confirmed that one of the main factors determining catalytic activity is the ease of reducibility in the absence of bulk-like CuO species. Finally, the long-term test revealed that the catalytic activity and stability remained constant under a high concentration of CO₂ in the feed gas for 19 h with an average CO conversion of 61.83%.

• Clean Technology
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• v.24 no.1
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• pp.50-54
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• 2018

In this work, N-methyl-2-pyrrolidone (NMP) was added into diethylenetriamine (DETA) aqueous solution for high $CO_2$ loading via phase splitting of absorbents during $CO_2$ absorption. Immiscible two phases were formed in the range of more than 30 wt% of NMP in 2 M DETA + NMP + water absorbents because of low solubility of DETA-carbamate in NMP solution. As the composition of NMP in the absorbents increased, the difference of $CO_2$ loading between each phase increased and the volume of bottom phase decreased. In $CO_2$ absorption in packed column by 2 M DETA + NMP + water absorbents, the absorption rate decreased in the range of more than 40 wt% of NMP. It is due to the increasing of mass transfer resistance in liquid film of absorbents at the high concentration of NMP. DETA + NMP + water absorbent is expected as the promising one for reducing the regeneration energy of absorbents according to volume reduction of $CO_2-rich$ phase.

• Journal of the Korean Chemical Society
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• v.24 no.1
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• pp.1-7
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• 1980

Solvolysis rate constants for methylchloroformate, methylthionochloroformate, methylthiolchloroformate and methyldithiochloroformate have been determined conductometrically in methanol, ethanol and ethanol-water mixtures and activation parameters have been derived. Results show that methylchloroformate solvolyzes through $S_N2$ process while methyldithiochloroformate solvolyzes by $S_N1$ process in all the solvent systems. The rate of hydrolysis decreased in the order, $CH_3S(CS)Cl>CH_3S(CO)Cl>CH_3O(CS)Cl>CH_3O(CO)Cl$ which corresponds to the order of decreasing $S_N1$ character. In methanol, $CH_3S(CS)Cl$ solvolyzed via the $S_N1$ mechanism while the others solvolyzed via the $S_N2$ process. In ethanol, however, $S_N2$ character was dominant for all the compounds, except methyldithiochloroformate, for which $S_N1$ character was still strong enough to accelerate the rate of ethanolysis. In ethanol-water mixtures, $CH_3S(CS)Cl$ and $CH_3S(CS)Cl$ solvolyzed via $S_N2$ process in ethanol-rich region while the $S_N1$ character increased greatly in water-rich region for the solvolysis of these compounds. The order of $S_N1$ character for solvolysis in water-rich region was the same as the order of hydrolysis rate.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.09a
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• pp.331-334
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• 2002

탄산수내 REEs의 함량과 거동특성을 알아보기 위해 암석시료, 탄산수 및 침전물에 대한 REEs 분석을 실시하였다. 탄산수가 산출되는 인접지에서 채취한 암석시료들은 물의 유형에 따라 큰 농도변화를 보여주지 않으며, 대체적으로 LREEs가 부화된 특성을 보여주고 있다. 유형에 따른 탄산수의 REEs 농도변화는 서로 상이한데, Na-HCO$_3$ 유형은 강한 HREE의 부화를 보여주지만, Ca-HCO$_3$ 유형은 HREE의 부화를 보여주지 않고 감소하는 경향을 보이며, 화학적으로 중간 유형에 속하는 Ca-Na-HCO$_3$ 유형 탄산수는 Eu을 제외하고는 전체적으로 flat한 분포를 보여준다. 탄산수에서 침전된 침전물과 침전물을 제거한 물의 REE의 유형은 침전물이 발생되기 전의 탄산수와 유사한 경향을 보이지만, 침전물의 발생으로 인한 특징적이고 강한 anomalies를 보여준다. 침전된 침전물의 REEs 특성은 침전물이 발생되기 전의 원 탄산수와 거의 유사한 분포특성을 보여준다. 반면에 침전물을 제거한 탄산수에서는 탄산염침전물의 침전과 연관되어 매우 강한 Eu anomalies를 보여주며, 대체적으로 HREE가 부화된 특성을 보여주었다. 탄산수내 가장 우세한 REE 종은 CO$_3$$^{2-}$ 종이며, CO$_3$$^{2-}$ 복합체 때문에 REEs의 분별작용 (HREE의 부화)이 일어나는 것으로 판단되 었다.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.6
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• pp.586-593
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• 2014

Limited sources of fossil fuels and also global climate changes caused by $CO_2$ emissions are currently discussed around the world. As a renewable, carbon neutral and widely available energy source, biogas is regarded as a promising alternative to fossil fuels. In this study, a plasma dump reformer was proposed to produce $H_2$-rich synthesis gas by a model biogas. The three-phase gliding arc plasma and dump combustor were combined. Screening studies were carried out with the parameter of a dump injector flow rate, water feeding flow rate, air ratio, biogas component ratio and input power. As the results, methane conversion rate, carbon dioxide conversion rate, hydrogen selectivity, carbon monoxide yield at the optimum conditions were achieved to 98%, 69%, 42%, 24.7%, respectively.

• Journal of agriculture & life science
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• v.45 no.4
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• pp.105-112
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• 2011

Nutritional components and antioxidant activities of commercial loquat leaf tea (CLLT) were evaluated. Proximate compositions were as follows; moisture 5.34%, crude protein 8.38%, crude fat 13.26%, nitrogen free extract 46.21%, crude fiber 19.24% and crude ash 7.57%, respectively. Ascorbic acid and total phenolics content of CLLT was 0.47 mg/100 g and 42.55 mg/GAE g, respectively. Mineral elements were Ca 1,624.01 mg/100 g, K 1,099.66 mg/100 g, and Mg 192.70 mg/100 g, respectively. Amino acid contents of CLLT were very rich in glutamic acid 565.98 mg/100 g and deficient in cystine 12.97 mg/100 g. The 2,2'-azino-bis (3-ethylbenzthiazoline-6- sulfonic acid) diammonium salt (ABTS), 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities of hot water extract from CLLT were 72.51% and 90.11%, respectively at a concentration of $1,000{\mu}g/mL$. Reducing power and ferric reducing antioxidant power (FRAP) of hot water extract from CLLT were increased in a dose dependent manner. Therefore, these results suggest that the hot water extract of CLLT possess antioxidant activities and thus it has great potential as a source for functional food such as natural antioxidant.